1. Field of the Invention
The present invention relates to a camera module, and, more particularly to a camera module having a structure for preventing electromagnetic waves generated in the camera module from being emitted out of the camera module and preventing external electromagnetic waves and noise from being introduced into the camera module, wherein the structure is simplified without using additional parts, whereby assembly of the camera module is improved, the manufacturing costs of the camera module are reduced, and the size of the camera module is decreased.
2. Description of the Related Art
Generally, a camera module comprises a lens unit including at least one lens, a housing in which the lens unit is mounted, a sensor unit including an infrared (IR) filter and an image sensor, and a protection unit for shielding the image sensor.
FIG. 1a is an exploded perspective view illustrating a conventional camera module, and FIG. 1b is an assembled perspective view illustrating the conventional camera module. As shown in FIGS. 1a and 1b, a lens unit 110 comprises a lens 112, a barrel 114 in which the lens 112 is mounted, and a cap 116 disposed at the outer circumferential surface of the upper end of the barrel 114, the cap 116 having an incident hole 116a formed through the center of the upper surface thereof.
It should be noted that two or more lenses 112 might be mounted in the barrel 114 based on function and performance of the camera module to be realized.
Preferably, the cap 116 is fitted on the outer circumferential surface of the upper end of the barrel 112 in a threaded engagement fashion such that the opened upper end of the barrel 114 is partially blocked by the cap 116 so as to prevent the lens 112 mounted in the barrel 114 from being separated from the barrel 114.
A housing 122 has an inner hole 124 for accommodating the barrel 114. The inner hole 124 is provided at the inner circumferential surface thereof with a female thread part 124a, which is threadly engaged with a male thread part 114a formed at the outer circumferential surface of the barrel 114 such that the barrel 114 is securely mounted in the inner hole 124, and thus, the lens unit 110 is securely mounted in the housing 122 in a threaded engagement fashion. As a result, the barrel 114 can be moved relative to the housing 122, which is stationary, in the direction of an optical axis.
Under the housing 122 is disposed a sensor unit 130, which focuses an image of a subject introduced through the lens 112 and converts the focused image into an electric signal.
To this end, the sensor unit 130 comprises an image sensor 132, an infrared (IR) filter 134 and a circuit board 136. The image of the subject introduced through the lens 112 is partially filtered by the IR filter 134, and is then sensed by the image sensor 132.
The image sensor 132 is electrically connected to the circuit board 136, such as a flexible printed circuit board (FPCB), which is an image signal transmitting device. Consequently, the image of the subject sensed by the image sensor 132 is converted into an electric signal by the image sensor 132, and is then transmitted to a display unit (not shown), such as a liquid crystal display (LCD), through the circuit board 136 such that the image is displayed on the display unit.
A protection unit 140, which shields the image sensor 132 for preventing injurious electromagnetic waves from being emitted out of the camera module, comprises: an upper shield can 141 mounted to the housing 122; and a lower shield can 142 having engagement protrusions 144, which are resiliently engaged in engagement holes 143 formed at the upper shield can 141.
Consequently, electromagnetic waves generated from the image sensor 132 are prevented from being emitted out of the camera module by the protection unit 140 comprising the upper and lower shield cans 141 and 142. As a result, the electromagnetic waves are prevented from affecting electronic parts adjacent to the camera module, and therefore, inducing communication jamming.
Preferably, the circuit board 136 is coated with silver paste or is formed with a ground wire. In this case, the silver paste prevents external noise or external electromagnetic waves from being introduced into the circuit board 136 such that the external noise or the external electromagnetic waves do not affect the circuit part of the circuit board 136. The external noise or the external electromagnetic waves are transmitted out of the circuit board 136 through the ground wire formed at the circuit board 136. As a result, communication jamming due to the external electromagnetic waves and malfunction of the circuit due to the external noise are effectively prevented.
However, the protection unit 140 is divided into the upper and lower shield cans 141 and 142, which are made of metal, and therefore, it is necessary to assemble the protection unit 140 such that the image sensor 132 is shielded by the protection unit 140 in an additional assembly line. As a result, the number of components of the camera module is large, and the assembly process is complicated, which deteriorates productivity of the camera module. Furthermore, it is difficult to decrease the size of the camera module according to demand for miniaturization.